Precision surgery on microscaled worms (C. Elegans)
is quite a challenge; its about 1 mm in length. A research team from
the University of Texas at Austin developed a method of laser-assisted
surgery to work on these little beasts, being able to section a single
axon (the "arms" of a neuron) with great precision : An
ultra-short pulse laser that can perform extremely precise surgery on
tiny roundworms may be the key to understanding nerve regeneration and
is an important step toward treatment of human neurological disease,
according to research published in the Dec. 16 issue of Nature.

Dr.
Adela Ben-Yakar, an assistant professor of mechanical engineering at
The University of Texas at Austin, led the development of the
technique. It acts like a pair of tiny “nano-scissors,?able to cut,
for example, nano-sized units like nerve axons, the parts of nerve
cells that carry nerve impulses away from the cells to muscles or to
other cells.
“This tool opens up a new frontier for biologists studying nerve
regeneration,?says Ben-Yakar. “We can also apply it to many other
studies that require nanosurgery, so it’s a very versatile tool.?The beauty of this laser, she says, is its ability to cut organelles
(parts of cells—they are what organs are to organisms) precisely,
without damaging surrounding tissue. Usually, conventional lasers used
in surgery heat the area to be cut, then cut it, but this heightens the
risk for tissue damage.
Ben-Yakar’s nanosurgery technique used a series of low-energy
“femtosecond?laser pulses to partially sever the axons of several
anesthetized C. elegans, a widely studied type of roundworm about one
millimeter long. A femtosecond is one millionth of a billionth of a
second.
“The time is very important here,?she says. “Because it happens so
fast, there isn’t enough time for heat to diffuse out, so we don’t
damage anything. The pulse’s very s
hort length makes the photons in the
laser concentrate in one area, delivering a lot of power to a tiny,
specific volume without damaging surrounding tissue.?Once cut, the axons vaporized, and no other tissue was harmed.
To assure the axons were actually cut, and their disappearance wasn’t
caused by discoloration by the laser, the researchers cut axons they
knew would impair the worms?backward motion. The worms couldn’t move
backwards after surgery. But within 24 hours, most of the severed axons
regrew and the worms recovered backward movement—confirming that the
precision of the laser’s cut didn’t damage surrounding tissue and
allowed the neurons to grow a new axon to reach the muscle. Until now,
researchers have only been able to investigate nerve regeneration in
mice and zebrafish, which have complex nervous systems. This laser
allows researchers to study nerve cells at their most basic
evolutionary form, opening the door to other experiments on genetic and
molecular factors that determine whether damaged nerve cells regrow.
Ben-Yakar developed the femtosecond laser surgery technique using the
laboratories and equipment of Dr. Robert Byer, a Stanford University
professor, while doing post-doctoral work. The paper’s other co-authors
are Mehmet Fatih Yanik at Stanford, Hulusi Cinar, Hediye Nese Cinar and
Andrew D. Chisholm at the University of California at Santa Cruz and
Yishi Jin of UC Santa Cruz and the Howard Hughes Medical Institute.
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